This is like the hardest thread to answer. They are EXTREMELY similar. Except for the SFX.
The SR-71 and HP are both metal rimmed yoyos where there is a large amount of metal more than plastic, different than just the metal rimmed. SFX is great, as in these few days, I’ve heard many good things about it.

I feel that the HP is just too wide, as the feel too, so I prefer SR-71.